Orthographic Projection Issue

[nickyc95]

I have a problem with my Ortho Matrix. The engine uses the perspective projection fine but for some reason the Ortho matrix is messed up. (See screenshots below).

Can anyone understand what is happening here?

At the min I am taking the Projection matrix * Transform (Translate, rotate, scale) and passing to the Vertex shader to multiply the Vertices by it.

void Matrix4f::InitOrthoProjTransform(float left, float right, float top, float bottom, float zNear, float zFar)
{
    m[0][0] = 2 / (right - left);   
    m[0][1] = 0;                        
    m[0][2] = 0;                        
    m[0][3] = 0;

    m[1][0] = 0;                        
    m[1][1] = 2 / (top - bottom);   
    m[1][2] = 0;                        
    m[1][3] = 0;

    m[2][0] = 0;                        
    m[2][1] = 0;                        
    m[2][2] = -1 / (zFar - zNear);  
    m[2][3] = 0;

    m[3][0] = -(right + left) / (right - left);
    m[3][1] = -(top + bottom) / (top - bottom);
    m[3][2] = -zNear / (zFar - zNear);
    m[3][3] = 1;
}

This image shows the Perspective projection:

Persp

2Untitled-1.png (12.12 KiB) Viewed 3027 times

Then the Orthographic projection (InitOrthoProjectionTransform(0.0f, 800.0f, 0.0f, 600.0f, 0.1f, 1000.0f) )
(I'll upload a video to demonstrate what is happening.)

Ortho

1Untitled-1.png (14.67 KiB) Viewed 3027 times

VIDEO Shows the same scene, rotating on the Y axis.
http://youtu.be/2feiZAIM9Y0

[X Abstract X]

Try these 2 changes:

void Matrix4f::InitOrthoProjTransform(float left, float right, float top, float bottom, float zNear, float zFar)
{
    m[0][0] = 2 / (right - left);   
    m[0][1] = 0;                        
    m[0][2] = 0;                        
    m[0][3] = 0;

    m[1][0] = 0;                        
    m[1][1] = 2 / (top - bottom);   
    m[1][2] = 0;                        
    m[1][3] = 0;

    m[2][0] = 0;                        
    m[2][1] = 0;                        
    m[2][2] = -2 / (zFar - zNear);  
    m[2][3] = 0;

    m[3][0] = -(right + left) / (right - left);
    m[3][1] = -(top + bottom) / (top - bottom);
    m[3][2] = -(zFar + zNear) / (zFar - zNear);
    m[3][3] = 1;
}

[nickyc95]

Try these 2 changes:

void Matrix4f::InitOrthoProjTransform(float left, float right, float top, float bottom, float zNear, float zFar)
{
    m[0][0] = 2 / (right - left);   
    m[0][1] = 0;                        
    m[0][2] = 0;                        
    m[0][3] = 0;

    m[1][0] = 0;                        
    m[1][1] = 2 / (top - bottom);   
    m[1][2] = 0;                        
    m[1][3] = 0;

    m[2][0] = 0;                        
    m[2][1] = 0;                        
    m[2][2] = -2 / (zFar - zNear);  
    m[2][3] = 0;

    m[3][0] = -(right + left) / (right - left);
    m[3][1] = -(top + bottom) / (top - bottom);
    m[3][2] = -(zFar + zNear) / (zFar - zNear);
    m[3][3] = 1;
}

Hi, thanks for the reply.

Changing the ortho matrix to the one you have posted still hasn't fixed the issue.

Thanks

[X Abstract X]

What are the results if you omit using any model or camera transforms and multiply the vertices of an on-screen quad by just the ortho matrix?

[nickyc95]

What are the results if you omit using any model or camera transforms and multiply the vertices of an on-screen quad by just the ortho matrix?

Hi there,

Turns out my math class isn't pristine

I was swapping conventions from the actual math class and the orthographic matrix.

I just have to ensure I am more constant with the conventions that I use.

Thank you